Why are Joist dimensions are different?

I purchases 2x8x10 joist lumber from two different places. It turned out the actual joist dimensions are different. Some are 7 1/8" and some are 7 1/2". I used the shorter one to build the outer joist. The length of the deck will 12 feet wide. Is the height difference acceptable?

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Dec 01, 2012
Probably one is wetter than the other
by: John

It is possible but unlikely that the lumber was milled at different mills. The more typical reason for the joists sizes being different, is that the narrower board is much drier. I would bet that it was originally 7-1/2" also.

Some species like southern pine which has very large growth rings can move a lot as it dries out. Did you notice if one was wetter and heavier (the larger one)?

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